A shell casing left behind at a San Antonio 7-Eleven during a robbery attempt was the proof investigators needed to arrest a suspect, police said in an arrest affidavit.

Manuel Delgado, 25, was arrested Tuesday by San Antonio police in connection to November 2017 robbery reported in the 2300 block of West Avenue.

The store clerk told responding officers a man and woman came into the store and grabbed multiple cans of alcoholic drinks. Video surveillance showed the two run out of the store with the drinks, according to the affidavit.

The clerk ran after them and struggled with the woman to get the drinks back. During the struggle, a third suspect pulled out a gun fired it toward the clerk, helping the robbers escape.

The casing left behind was entered in the National Integrated Ballistic Information Network, which is run by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The bullet matched one left behind in the 1100 block of Castroville Road in a December 18, 2017 incident, according to the affidavit. In that incident, Manuel Delgado was arrested for a weapons violation with a black handgun.

Along with witness statements, the evidence helped police obtain an arrest warrant for Delgado.

He is charged with aggravated robbery. His bail was set at $50,000, according to jail records.

Police have identified two other suspects in the robbery but it was not immediately clear if they've been charged.

Fares Sabawi covers crime in San Antonio and Bexar County for mySA.com. Read more of his stories here. | fsabawi@mysa.com | Twitter: @FaresInSA